The invention generally relates to a wireless communication network, and more particularly, relates to an improved home location register (HLR) that provides switch capability mediation between different mobile switching centers (MSCs) in a wireless communication network.
Wireless communication is one of the fastest growing segments of the telecommunication industry. With the mobility of the wireless devices, such as cellular phones and pagers, a subscriber to a wireless service can make or receive a call or receive a message without being restricted to any particular location. Because of the convenience provided by wireless devices, they have been widely used by average consumers.
Wireless communications are provided through a wireless communication network, which can be realized, for example, as a Signaling System 7 (SS7) network. The SS7 network uses the EIA/TIA Interim Standard 41 (IS-41) protocol, which is the standard commonly used in North America. A description of the SS7 network and the IS-41 protocol can be found in Signaling System #7, by Travis Russell, and The Mobile Communications Handbook, by Jerry Gibson, which are hereby incorporated by reference.
The SS7 network is used for switching data messages pertaining to connecting telephone calls and for maintaining the signaling network. As shown in FIG. 1, the SS7 network 100 has three different types of nodes or signaling points: Service Switching Point (SSP) 112, Signal Transfer Point (STP) 116, and Service Control Point (SCP) 122.
An SSP 112 is an local exchange in the telephone network. An SSP 112 uses the information provided by the calling party (such as dialed digits) and determines how to connect the call. An STP 116 serves as a router in the SS7 network and switches SS7 messages as received from the various SSPs 112 through the network to their appropriate destinations. An STP 116 receives messages in packet form from an SSP 112. These packets are either related to call connections or database queries for an SCP 122. If the packet is a request from an SSP 112 to connect a call, the message must be forwarded to the destination where the call will be terminated. The destination is determined by the dialed digits. If the message is a database query seeking additional information regarding a person who subscribes a wireless service, i.e., a "subscriber", the destination will be a database. Access to telephone company databases is provided through an SCP 122. These databases are used to store information about subscribers' services, calling card validation, fraud protection, etc.
As shown in FIG. 1, the wireless network is shared by multiple regions 126, such as regions A and B. In each region 126, an SCP 122 is provided. Each region 126 is further divided into a number of registration areas 132, each of which is served by a Mobile Switching Center (MSC) 136. An MSC 136 provides wireless communication services to all properly registered cellular phones 142 in the registration area.
As illustrated in FIG. 1, an SCP 122 contains an authentication center (AC) 146 and a home location registers (HLR) 152. AC 146 authenticates a subscriber's cellular phone through the use of an encrypted number called the A-Key. HLR 152 is used to store information regarding cellular subscribers in the region for which it provides services. HLR 152 also stores information identifying the services allowed for each subscriber. In addition to these, HLR 152 stores the current locations of cellular phones 142 of those subscriber's who initially activated their cellular phones through a wireless service provider in the region the HLR serves. This region is also referred to as the "home area" of those subscribers. Although not shown, a backup HLR is also provided in SCP 122.
A visitor location register (VLR) 156 is also provided in each region 126. VLR 156 is used when a cellular phone 142 is not recognized by a local MSC. VLR 156 stores the current locations for the visiting subscribers.
Typically, in conventional wireless communication network, the MSCs in regions A and B may be provided by different vendors, e.g., AT&T, Ericsson, Motorola, or Northern Telecom, etc. These different MSC vendors implement the capabilities of their MSCs in different ways. Furthermore, the MSCs provided by some vendors, such as Northern Telecom, may have proprietary features not included in other vendors' MSCs. Even the MSCs provided by the same vendors may implement different revisions of IS-41, e.g, IS-41 Rev A, IS-41 Rev B, etc. Thus, it may present a problem when a subscriber travels from his home area where he initially activated his cellular phone to a roaming area, such as from region A to region B in FIG. 1. If a call origination request is received by an MSC in region A, i.e., the home area of the subscriber's cellular phone and this MSC attempts to communicate with the MSC currently serving the subscriber in region B, there may be difficulties in connecting the call if the two MSCs implement different capabilities. The call may not even be deliverable to the subscriber currently in region B. This would create a serious problem for the subscriber since he may not have expected that the communication cannot go through as intended when he is in region B. Conventional HLRs provide minimum support between various kinds of MSCs.
Accordingly, there is a need for an improved HLR that can provide switch capability mediation between two MSCs implementing different capabilities so that the communication between the two MSCs may be optimized.